Oxygenated organic compounds of improved odor



United States Patent 3,271,456 OXYGENATED ORGANIC COMPOUNDS OF IMPROVEDODOR Elaine Theodora Delaune and John Cecil Winkler, Baton Rouge, La.,assignors to Esso Research and Engineering Company, a corporation ofDelaware No Drawing. Filed Mar. 26, 1962, Ser. No. 182,639 8 Claims.(Cl. 260-593) The present invention relates to a method of improving theodor of contaminated oxygenated chemicals, especially lower molecularweight alcohols and ethers and the improved chemicals obtained by saidmethod.

Most of the alcohols, ethers and ketones made by commercial methods haveforeign odors which, depending on their strength and distastefulness,limit the end use of these oxygenated organic substances. For example,odor is an important characteristic in alcohols used in food, drugs andtoilet articles. Likewise, ethers that might otherwise be utilized asanesthetics are frequently rejected on the basis of poor odor.

Considerable work has been carried out in the past in an attempt to makecontaminated alcohols, ethers, etc. satisfactory for use in productswherein odor is a critical property. Fractional distillation methodshave failed to accomplish the desired result because the odor-impartingcontaminant is usually present in relatively small quantities andfrequently boils in the same range as the oxygenated organic product.Efforts along other lines, such as the addition of potassium hydroxide,have similarly been unsuccessful in improving the odor quality of theabove-mentioned chemicals.

It has now been discovered that trace amounts of certain phenoliccompounds have a marked effect on the odor quality of biologically andsynthetically prepared oxygenated products. One advantage of using smallquantities of these additives is that they do not noticeably contaminatethe product. For instance, when these additives are employed inconcentrations of 1 or 2 p.p.m., the oxygenated chemicals will stillpass the standard test methods used by the various industries; whereasother additives that have been experimented with heretofore, to beeffective, must be used in such large amounts that they interfere withthese tests.

The following is a structural formula which broadly defines theadditives that come within the purview of the invention:

wherein R and R represent hydrogen or an alkyl radical, either straightor branched chain, containing 1 to 16 carbon atoms, preferably 1 to 5carbon atoms, and R R and R represent hydrogen or an organic radical,either cyclic, straight or branched chain, having 1 to 16 carbon atoms,preferably 4 to carbon atoms, selected from the group consisting ofalkyl and aroxy radicals; at least one of said R radicals represents analkyl or aroxy group.

Among the phenolic compounds that can be used to improve the odorcharacteristic of organic oxygenated chemicals in accordance with thepresent invention are polyalkylated phenols such as 2,6-ditertiary-butylpara-cresol, 2,4-ditertiary-butyl phenol, 2-methyl-4-tertiary-butylphenol, 2,6-dimethyl phenol, and

Patented Sept. 6, 1966 2,4-ditertiary-butyl-6-methyl phenol; andbis-phenol alkanes such as 4,4-methylene-bis-(2,6-ditertiary butylphenol),

2,2'-bis(p-hydroxyphenyl) propane,

4,4'-bis(2,6-ditertiary butyl phenol),

4,4-methylene-bis-(6-tertiary-butyl-o-cresol) and 2,2-methylene-bis-(4-methyl-6-tertiary-butylphenol).

It has been found that the most effective additives are those thatpossess a single phenol nucleus and have 2 or 3 straight or branchedhydrocarbyl groups attached to the ortho, and/or para positions of thearomatic ring. Of the foregoing, the lower diand tri-alkyl substitutedphenol compounds are preferred. These compounds are represented by thefollowing formula:

wherein R is a lower alkyl group having 1 to 5 carbon atoms, and R and Rare either hydrogen or lower alkyl groups having 1 to 5 carbon atoms.Usually one of the alkyl substituents is methyl and one or both of theothers is tert-butyl. The other phenolic substances improve the odor ofthe product, but generally their effect is not as great.

In accordance with the present invention, a minute quantity of one ormore of the organic additives is admixed with an oxygenated chemicalhaving an undesirable alien odor. It is advisable to limit theconcentration of additive to not more than about 10 p.p.m. (parts permillion) in order to avoid further contamination of the product andpossible interference with other tests which the chemical may have topass in order to be suitable for a particular end use. It has been foundthat while as little as 0.01 p.p.m. (by wt.) has a beneficial result onthe odor quality of the substrate, best results are obtained when about0.5 to 5 p.p.m. (by wt.) are employed. In the case of the para-cresoladditives, it is usually not necessary to add more than about 1 or 2p.p.m. in order to make the oxygenated product suitable for mostpurposes.

The odor improving agent can be contacted with the monohydric alcohol orother substance by simply mixing the two materials at room temperature.In some instances, it is advantageous to dissolve the additive in aportion of the liquid product in order to facilitate mixing and insure ahomogeneous product.

Ambient temperature is eminently suitable for the addition of the agentto the contaminated product. However, higher and lower temperatures maybe used. Broadly speaking, temperatures ranging from about 0 C. up tothe boiling point of the oxygenated product can be employed withsuccess. Pressure, of course, is not a critical condition and,therefore, for economic reasons, substantially atmospheric pressureshould be used in the treatment of the oxygenated product.

The improvement in odor quality is almost instantaneous and remains fora considerable period of time. In fact, in the case of certain products,particularly isopropanol, even greater improvements are obtained byallowing the treated sample to age for several months at roomtemperature.

The oxygenated chemicals that can be improved by means of the presentinvention include primary and secondary alcohols, ethers and ketones.While the use of these additives has application to the higher molecularweight products, they find their greatest use in the treatment ofsubstantially pure lower molecular weight substances such as ethanol,isopropanol and diethyl ether.

The oxygenated substances are generally aliphatic compounds that areeither saturated or unsatunated and contain from 1 to 16 carbon atoms,preferably 2 to 4 carbon atoms, per molecule. Among the products thatcan be improved by the above-described treatment are water solubleprimary; secondary and tertiary monohydric alcohols, "such as methanol,ethanol, tertiary butanol, isopropanol and secondary butanol, derivedfrom petroleum hydrocarbons; highly branched oxo alcohols such as decylalcohol, hexadecyl alcohol and isooctyl alcohol; alkyl oxides such asdiethyl ether, divinyl ether, methyl ethyl ether and diisopropyl ether;and ketones such as methyl ethyl ketone, methyl isobutyl ketone andacetone.

The phenolic additives will reduce or eliminate substantially all of thevarious types of extraneous odors commonly found in oxygenated organicproducts. For instance, in the case of alcohols made by hydratingolefins via the formation of sulfate esters, aldehyde, ketone, sulfurand butyl odors are frequently detected in the finished product. Thehydrocarbyl-substituted oresol compounds are especially effective in theelimination of the aforementioned odors.

One method of evaluating the redolent property of a product is toprepame samples having graduated odor intensities that can be used todetermine the strength of the odor in the oxygenated organic product. Inone such method, the standard samples are assigned the values rangingfrom 1 to 12; the highest number representing the sample having thestrongest odor. In this test, a mating of 6 is designated acceptable.This does not mean that the product can be employed for all purposessince, obviously, some end uses require essentially odorfree materials.In such cases, the product cannot have a rating greater than 2 andpreferably has a rating of 1? In other words, it must be substantiallyfree of objectionable odors.

The following examples are given to provide a better understanding ofthe invention.

Example 1 In order to demonstrate the effectiveness of even traceamounts of the phenolic additives on the odor characteristic ofalcohols, various samples of 95 vol. percent ethanol prepared by thehydration of ethylene obtained from a C petroleum fraction, were treatedwith l p.p.m. of 2,6-ditertiary-butylpara-cresol. The cresol compoundwas dissolved in the alcohol samples with stirring at room temperatureand atmospheric pressure. Then the samples were rated by a panel ofthree using the test method described above. None of the panelists knewwhich were the treated samples. The results are set forth in the tablebelow.

EFFECT OF ADDING 1 P.P.M. OF 2, G-DITERTIARY-BUTYL PARA-ORESOL ON ODOROF ETHANOL SAMPLES Sample No l 2 3 4 Rating Control 10A 12A 8B 12 {-RdzATreated 3A 3A 2G 3A Example 2 A sample of vol. percent isopropanolhaving an odor rating of 8 was treated in the manner described inExample 1 with 1 p.p.m. of 2,6-ditertiary-butyl paracresol. The treatedsample had an odor rating of 6, thus making it acceptable for use in anumber of products.

Example 3 A sample of diethyl ether prepared from ethylene was treatedin the manner described in Example 1 with 2 p.p.m. of2,6-ditertiary-butyl para-cresol. The control sample had an odor ratingof 8 HB (high boilers), while the treated ether had a rating of 3.

Example 4 Essentially pure methyl ethyl ke-tone having an odor rating of12A (sour odor) was mixed with 1 p.p.m. of 2,6-ditertiary-butylpara-cresol at room temperature, and its odor was thereby reduced to 6A.

Example 5 A 95 vol. percent ethanol sample having an odor rating of 12-Awas treated Woth 1 p.p.m. of 2,6-ditertiary-butyl para-cresol at roomtemperature. The treated ethanol had an acceptable odor, and,furthermore, its permanganate time, which is a measure of the reducingsubstances present in the alcohol, was about the same as the control.However, when another sample of the same ethanol was treated with 10p.p.m. of the p arracresol compound, the permanganate time decreasedfrom about 30 minutes to 10 minutes. Thus, while '10 p.p.m. or more ofthese phenolic additives will improve the odor characteristic of theoxygenated products, large amounts interfere with the permanganate timeand other specification tests. It has been found that about 1 or 2p.p.m. of these additives can be utilized without causing them to failthe other tests to which the products may be subjected. Larger amounts,i.e. up to about 10 p.p.m., of the phenolic compounds can be used whereodor is the only important characteristic.

Example 6 Sample #1 in Example 1 was treated with 3 p.p.m. of4,4-methylene-bis-(2,6-ditertiary butyl phenol) in place of thepara-cresol compound. The odor rating of the treated ethanol wasimproved to a 6-A class.

Example 7 A sample of diethyl ether having an odor rating of 8 HB wastreated by dissolving 5 p.p.m. of 4,4-methylene-bis(2,6-ditertiary butylphenol) in it at room temperature and atmospheric pressure, and stirringthe resulting mixture for about a minute. The treated product had a moreacceptable odor, i.e. 4 HB.

Example 8 A sample of methyl ethyl ketone having an odor rating of 12A(sour) was treated by dissolving 1 p.p.m. of4,4'-methyIlene-bils(2,6aditertiatry butyl phenol) in. it at roomtemperature and atmospheric pressure, and stirring the resulting mixturefor 1 minute to insure a homogeneous solution. The treated product had amore acceptable odor rating of 8-A.

Example 9 Example 10 Example 9 was repeated except 3 p.p.m. of4,4-methylene-bis(2,6-ditertiary butyl phenol) Was used. The.

treated tertiary butyl alcohol product had an odor rating of (no sourodor present).

Example 11 A sample of secondary butyl alcohol having an odor rating of12+ (heavy aldehyde-type odor) was treated by dissolving 5 p.p.m.2,6-ditertiary butyl p-cresol in it at room temperature and atmosphericpressure and stirring the resulting mixture for 1 minute. The treatedproduct had an odor rating of 10 (very little of the heavy aldehyde odorremained).

Example 12 A sample of acetone having an odor rating of 12+A is treatedby dissolving 8 p.p.m. of 4,4'-methylene-bis (2,6-ditertiary butylphenol) in it at room temperature and atmospheric pressure and stirringresulting mixture for 1 minute. The treated product had a moreacceptable odor, i.e. 10A.

Example 13 Example 12 was repeated except 3 p.p.m. of 2,6-ditertiarybutyl p-cresol was used. The treated product had a more acceptable odor,i.e. 10A.

Example 14 A sample of 95 vol. percent ethanol, having a disagreeableodor, is treated at room temperature by mixing it with 10 p.p.m. of2-methyl-4-tertiary butyl phenol. Its odor is substantially improved.

Example 1 5 Similar results to those described in Example 14 are gottenwhen odorous ethanol is mixed with 10 p.p.m. of 2,6-dimethy1 phenol.

Example 16 A sample of vinyl ether having a disagreeable hydrocarbonodor was mixed with 50 p.p.m. (wt.) of 2,6-ditertiary butyl-p-cresol andit was noted that the odor was much less after the addition of thecresol compound.

It is not intended to restrict the invention to the foregoing exampleswhich are given merely to demonstrate some of the embodiments of theinvention. It should only be limited by the appended claims in which itis intended to claim all the novelty inherent in the invention, as wellas all of the modifications and equivalents coming within the scope andspirit of the discovery.

What is claimed is:

1. A composition of matter comprising an oxygenated organic liquidselected from the group consisting of methanol, ethanol, tertiarybutanol, isopropanol, secondary butanol, branched oxo alcohols having 1to 16 carbon atoms per molecule, diethyl ether, methyl ethyl ether,diisopropyl ether, methyl ethyl ketone, methyl isobutyl ketone, andacetone having dissolved therein 0.5 to 5 p.p.m. of an alkyl-substitutedphenol compound having the structural formula wherein R is a C to Calkyl group and R and R are selected from the group consisting ofhydrogen and C to C alkyl groups.

2. A composition matter as defined in claim 1 in which thealkyl-substituted phenol compound is 2,6-ditertiary butyl cresol.

3. A composition of matter as defined in claim 1 in which the oxygenatedorganic liquid is .isopropanol and the alkyl-substituted phenol compoundis 2,6 ditertiary butyl cresol.

4. A composition of matter as defined in claim 1 in which the oxygenatedorganic liquid is diethyl ether and the alkyl-substit-uted phenolcompound is 2,6-ditertiary butyl cresol.

5. A composition of matter as defined in claim 1 in which the oxygenatedorganic liquid is methyl ethyl ketone and the alkyl-substituted phenolcompound is 2,6- ditertiary butyl cresol.

6. A composition of matter as defined in claim 1 in which the oxygenatedorganic liquid is tertiary butyl alcohol and the alkyl-substitutedphenol compound is 2,6- ditertiary butyl cresol.

7. A composition of matter as defined in claim 1 in which the oxygenatedorganic liquid is secondary butyl alcohol and the alkyl-substitutedphenol compound is 2,6- ditertiary butyl cresol.

8. A composition of matter comprising ethanol containing a trace amount,not exceeding about 2 p.p.m., of 2,6-ditertiary-butyl para-cresol.

References Cited by the Examiner UNITED STATES PATENTS 5/1954 Rosenwald260632.5X 6/1960 Leis et al. 26061l.5

Morawetz, Ind. & Eng. Chem., vol. 41 (1949), pages 14421447.

LEON ZITVER, Primary Examiner.

B. HELFIN, H. T, MARS, Assistant Examiners.

1. A COMPOSITION OF MATTER COMPRISING AN OXYGENATED ORGANIC LIQUIDSELECTED FROM THE GROUP CONSISTING OF METHANOL, ETHANOL, TERTIARYBUTANOL, ISOPROPANOL, SECONDARY BUTANOL, BRANCHED OXO ALCOHOLS HAVING 1TO 16 CARBON ATOMS PER MOLECULE, DIETHYL ETHER, METHYL ETHYL ETHER,DIISOPROPYL ETHER, METHYL ETHYL KETONE, METHYL ISOBUTYL KETONE, ANDACETONE HAVING DISSOLVED THEREIN 0.5 TO 5 P.P.M. OF AN ALKYL-SUBSTITUTEDPHENOL COMPOUND HAVING THE STRUCTURAL FORMULA